Liquid chromatography involves the spatial separation of different sub phases (compounds or components) of a sample due to the different affinity of these sub phases with an absorbent. A typical liquid chromatography system might comprise a separation column filled with the absorbent (such as very fine powder, for example), a mechanism for discharging a liquid sample, a pump for forcing one or more liquid solvents and the liquid sample to and through the column, and a detector sensitive to different physical characteristics of the sub phases as such are then passed through the column. Due to different respective affinity rates (absorption and desorption) of the different sample sub phases with the absorbent, these sub phases will be penetrated through the column and absorbent therein at different rates. This provides that the sub phases become isolated and axially spaced out as narrow bands, sequentially and separately passing the detector to be identified along with the possible determination of each's percentage within the sample. Generally only a small quantity of liquid sample need be used (a few mcls), and the volume of the column likewise can be small (perhaps only a few mls). It is preferred to pump the solvent to high pressures to pass at an accurate and substantially steady flow rate through the sample and into the column.
Thus, a typical analytical high performance liquid chromatographic system (HPLC) might be comprised of a high pressure pump, a sample injector, a column and a detector in a serial flow connection to a waste vessel. The pump is suited to deliver liquid solvent and sample to the column at pressures typically in the 500-4000 psi range. The injector allows the introduction via a syringe or the like of the liquid sample into the solvent stream while maintaining the high pressures in the system. The column causes a major pressure drop and provides for the above noted axial separation of desired components or analytes from the complex sample form. The detector distinguishes the analytes separated from the sample, yielding information of the existence, concentration and identity of such analytes in the sample.
My patent application Ser. No. 08/876,568, now U.S. Pat. No. 5,920,006 issued on Jul. 6, 1999, disclosed a High Performance Liquid Chromatography (HPLC) pumping, sample delivery and valving system oriented toward efficient use of small microbore short columns, satisfying the increasing trend toward converting HPLC methods to use less solvent and run faster. The system is compact and essentially unitary for space efficiency and ease of movement and set-up, is lightweight and inexpensive to make and use, and yet is reliable, accurate and versatile in use, and further will have an expected extended service life with minimal solvent leakage or potential damaging of the pump.
Thus, my patented system provides syringe type liquid delivery, with steady accurately controlled flow that could be reproduced for comparable test runs and reliable test conformations. It has a built-in injector port and mixing tee, eliminating many parts needed in other HPLC systems, and has positive valving (no check valves). The valving is powered by the pump powering motor, and its valving design minimizes wear and a need for frequent repair or replacement. Its low costs and convenience and simplicity of use can encourage HPLC participation by users having limited capital budgets, and multiple units can add HPLC system versatility. Its compactness and ease of set up and use can allow possible shipments for field use or for repair or maintenance, and/or for use as an optional OEM part in other LC or liquid handling systems. Its single stroke pumping capacity could satisfy solvent needs to complete most test runs (for example, 5 ml, to complete a 100 minute test run through a 1 mm ID column or a 25 minute test run through a 2 mm ID column), and could thereafter be easily and rapidly refilled for the next test run. Should extra volume capacity be needed, or for gradient elution tests, two or three like pumping and valving devices could be connected together as a unified system for doubling or tripling solvent volume or types.